Multi-walled Carbon Nanotubes Mixed Matrix Membranes
Mixed matrix membranes (MMMs) are important class of membranes prepared by incorporating nanosized fillers into polymer matrix. During this study Multiwalled carbon nanotubes (MWCNTs) are incorporated into poly(vinylidene fluoride) (PVDF), polyacrylonitrile (PAN), and poly(dimethylsiloxane) (PDMS) to fabricate MMMs. The incorporation of nanofillers is aimed to improve the separation performance and electrical properties of the membranes. Lack of dispersibility of MWCNTs in many common organic solvents is the major problem to obtain well dispersed MWCNTs in polymer composites. Surface functionalization provides a pathway where the surface chemistry of MWCNTs is altered by the introduction of chemical functional groups and improves their dispersion in different desired solvents and polymer matrices. PVDF MMMs are prepared by phase inversion method. The addition of MWCNTs to PVDF leads to the membranes with larger surface pore size but relatively low pore density compared to pure PVDF. PVDF MMMs do not show a significant improvement in separation performance and resistance against compaction. The introduction of MWCNTs leads to PVDF membranes exhibiting electrical conductivity. PAN MMMs are fabricated by phase inversion technique. The membranes incorporated with functionalized MWCNTs show better separation performance along with improved resistance against compaction at a maximum loading of 2 wt. % compared to purified MWCNTs containing membranes. PDMS MMMs are prepared by the solvent evaporation method. Functionalization of MWCNTs has remarkable influence on their dispersion in PDMS membranes. However, the addition of MWCNTs does not change the membrane separation performance significantly. Electrically conductive PDMS thin layered composite membranes are successfully prepared with the addition of MWCNTs.